Dyeing organic acid ester of cellulose textile materials with an aqueous solution of a normally acid-fading dyestuff, lower aliphatic alcohol, thiocyanate, and alkali metal hydroxide



Patented Jan. 31 1950 i DYEING ORGANIC ACID ESTER OF CELLU- LOSE TEXTILEMATERIALS 'WITH AN AQUEOUS SOLUTION OF A NORMALLY ACID-FADING IDYESTUFF, LOWER ALI- PHATIC ALCOHOL, THIOCYANATE, AND ALKALI METALHYDROXIDE Walter H. Hindle, Allentown, Pa., assignor to CelaneseCorporation of America, a corporation of Delaware No Drawing.Application October 10, 1946, Serial No. 702,363

8 Claims. (01. 859) This invention relates to the dyeing of textilematerials and relates more particularly to the dyeing of textilevmaterials made of or containing yarns having a basis of celluloseacetate or other organic acid ester of cellulose textile material.

.. a An object of this invention is the provision of an improved processfor the dyeing of cellulose acetate or other organic acid ester ofcellulose textile materials.

Another object of this invention is to provide an improved process forthe dyeing of cellulose acetate or other organic acid ester of cellulosetextile materials whereby dyed materials of improved resistance to acidfading may be obtained.

Other objects of this invention will appear from the following detaileddescription.

In dyeing cellulose acetate or other organic acid ester of cellulosetextile materials, excellent results may be obtained by employing. asolvent dyebath comprising an aqueous alcoholic solution 01 the desireddyestuff and applying said dyebath 'by mechanical impregnation methods.The dyebeen observed to exhibit a noticeable tendency to fade whenexposed to an acid atmosphere. {ittempts have been made to minimize thistendi'ency toward acid fading by subjecting the organic acid ester ofcellulose textile materials to certain after-treatments followingdyeing. Such after-treatments involve an additional manipulative stepand, since they increase the cost of the finished material, areuneconomical.

I I have now found that greatly improved resistance to acid-fading maybe imparted to cellulose acetate or other organic acid ester ofcellulose materials dyed by solvent dyeing methods if from 1 to 4 gramsper liter of an alkali metal hy- "droxide such as sodium hydroxide orpotassium hydroxide, for example, is incorporated in the alcoholicsolvent dyebath employed and the resulting dyebath then applied to saidcellulose acetate materials in any convenient manner. Any suitabledyeing method may be employed but padding or other form of mechanicalimpregnation yields the most advantageous results. Furthermore, I havefound that the addition of said alkali metal hydroxide to the solventdyebath not only improves the resistance of dyed cellulose acetatematerials to acid fading but yields deeper and heavier dyeings than areobtained by employing dyebaths containing the same concentration ofdyestuff but which do not contain added alkali metal hydroxide. i

The concentration of alkali metal hydroxide in the solvent dyebath iscritical since I have found that the addition of less than 1 gram perliter of alkali metal hydroxide to said dyebath does not produce anyincrease in the depth of dyeing nor any appreciable increase in theresistance of the dyed cellulose acetate material to acid fading.Furthermora'the use of a concentration of more than 4 grams per literdoes not yield the desired improvement and produces excessivesaponification. The optimum concentration within the aforementionedcritical limits depends, however, on the particular dyestufi employed.For certain dyestufis, the optimum concentration of alkali metalhydroxide is from 2 to 3 grams per liter while for others, aconcentration of from 3 to 4 grams per liter is most advantageous.

The lower aliphatic alcohols which are suitable for use in forming thesolvent dyebaths are those alcohols which are solvents for the dyestuffsemployed and which exert at least a swelling or softening action on theorganic acid ester of cellulose materials. While we prefer to employethyl alcohol in forming the dyebath, other alcohols such as methylalcohol, propyl alcohol, isopropyl alcohol, n-butyl alcohol, secondarybutyl alcohol, tertiary butyl alcohol, n-amyl alcohol, secondary amylalcohol and tertiary amyl alcohol, or mixture of these alcohols may beused. The amount of the alcohol used in the dye liquor will varydepending upon the alcohol or alcohols used. Optimum results areobtained when the lower aliphatic alcohol comprises at least I by weightof the dyebath.

As examples of inorganic swelling agents for the organic acid ester ofcellulose materials, there staple fiber yarns, or other may be mentionedthe salts of thiocyanic acid such as ammonium thiocyanate, sodiumthiocyanate, as well as other salts such as zinc thiocyanate. Optimumresults are achieved employing sodium thiocyanate. The inorganicswelling agent may be present in amounts of from 1 to 3% on the weightof the dyebath. Preferably, we employ from 1.5 to 2.5% by weight.

Various dyestuffs for organic acid ester of cellulose materials may beemployed in accordance with my novel process. These dyestuifs may beacid dyes which are ordinarily used for the dyeing of wool and which dovnot possess any substantial affinity for organic acid ester of cel-'lulose materials when applied by the methods usually employed forapplying said acid dyestufis, as well as those dyes which are relativelyinsoluble in water and which are usually applied I to organic acid esterof cellulose materials in the form of aqueous dispersions. Mixtures ofthese dyestuffs may also be employed. When these dyestuffs are appliedto organic acid ester of cellulose textile materials by mechanicalimpregnation methods in alcoholic solutions containing an inorganicswelling agent, and an alkali metal hydroxide, in accordance with myprocess, the resulting dyeings are not only faster to acid fading butare of increased depth and brilliance and may be obtained, as stated,with a relatively short immersion time. The washdown of the shade insubsequent washin and finishing operations is considerably less in thecase of fabrics dyed by our novel process than in the case of fabricsdyed by prior processes.

The amount of dyestuff dissolved in the dyebath will, of course, varywith the final shade desired in the material which is being dyed and maybe from as low as 0.01% up to 5.0% based on the weight of the materialto be dyed.

As stated, the dyebath may be applied to the organic acid ester ofcellulose textile materials by padding, spraying or by other convenientmethod of mechanical impregnation. Thus, as a continuous process, afabric may be unwound from a roll, passed through a solution of-thedyestufi, then between nipping rolls of a .pad ding mangle which areadjusted to permit the desired amount of dye liquor to be retained inthe fabric, and the fabric then subjected directly to washing orscouring. immersion of the fabric in the dye liquor isrelatively shortand may be from 1 to 6 seconds. If

desired, the fabric may be processed through the padding mangle atspeeds ranging up to 60 yards per minute. a

My process is applicable not only to the dyeing of fabrics butparticularly valuable results are obtained when other organic acid esterof cellulose textile materials such as staple fibers, in the form of atop, roving, or tow are dyed in accordance with my invention. Not onlymay faster and more uniform dyeings be obtained but, as in the case offabrics, increased production may be achieved along with a substantialreduction in the amount of dyestuff necessary to obtain a desired shade.1

The organic acid ester of cellulose fabrics, textile materials dyed inaccordance with my process may have a basis of cellulose acetate,cellulose propionate, cellulose butyrate, or of mixed esters such ascellulose acetate-propionate and cellulose acetatebutyrate. Thematerials may be mixed materials containing organic acid esters ofcellulose and yarns or fibers of other materials such as The duration ofthe A dyebath is prepared by dissolving 2000 grams of sodiumthiocyanate, 300 grams of sodium hyand 25 liters of water.

droxide and 500 parts by weight of Celliton Blue AF (a mixture of1-amino-4-anilido-anthraquinone and1-methylamino-4-anilido-anthraquinone) in a mixture of '75 liters ofethyl alcohol A cellulose acetate fabric of a satin weave ismechanically impregnated with this dyebath employing a suitable paddingmangle and the dyed fabric then washed and dried. The dyed fabricexhibits excellent fastness to acid fading on exposure for 40 hours toacid fumes in the usual standard testing cabinet. Fabric dyed with thesame dyebath but without sodium hydroxide being present fades to a hellounder the same conditions, and, in addition, is not dyed to as deep ashade as with the dyebath above wherein sodium hydroxide is added.Furthermore, when the concentration of sodium hydroxide in the dyebathis increased to 5 grams per liter, fabric dyed with said dyebath shows aconsiderable degree of fading. It is to be understood that the foregoingdetailed description is given merely by way of illustration and thatmany variations may be made therein without departin from the spirit ofmy invention. Having described my invention, what I desire to secure byLetters Patent is:

1.'Process for the coloration of organic acid ester of cellulose textilematerials, which comprises mechanically impregnating said organic .acidester of cellulose textile material with a solution of a dyestuff forthe organic acid ester of cellulose material, said dyestufif beingnormally subject to acid fading upon exposure to an acid atmosphere inan aqueous medium comprising a lower aliphatic alcohol, a salt ofthiocyanic acid which is a swelling agent for the organic acid ester ofcellulose material and from 1 to 4 grams per liter of an alkali metalhydroxide.

2. Process for the coloration of cellulose acetate textile materials,which comprises mechanically impregnating said cellulose acetate textilemate rial with a solution of a dyestuif for the cellulose acetatematerial, said dyestuff being normally subject to acid fading uponexposure to an acid atmosphere in an aqueous medium comprising a loweraliphatic alcohol, a salt of thiocyanic acid which is a swelling agentfor the cellulose 1 to 4 grams per liter of an alkali metal hydroxide.

3. Process for the coloration of organic acid ester of cellulose textilematerials, which comprises mechanically impregnating said organic acidester of cellulose textile material with a solution of a dyestufi forthe organic acid ester of cellulose material, said dyestuff beingnormally subject to acid fading upon exposure to an acid atmosphere inan aqueous medium comprising at least by weight of a lower aliphaticalcohol, a salt of thiocyanic acid which is a swelling agent for theorganic acid ester of cellulose material and from 1 to 4 grams per literof an alkali metal hydroxide.

4. Process for the coloration of cellulose acetate textile materials,which comprises mechanically impregnating said cellulose acetate textilematerial with a solution of a dyestuif for the cellulose acetatematerial, said dyestuff being normally subject to acid fading uponexposure to an acid atmosphere in an aqueous medium comprising at least60% by weight of a lower aliphatic alcohol, a salt of thiocyanic acidwhich is a swelling agent for the cellulose acetate material and from 1to 4 grams per liter of an alkali metal hydroxide.

5. Process for the coloration of cellulose acetate textile materials,which comprises mechanically impregnating said cellulose acetate textilematerial with a solution of a dyestufl" for the cellulose acetatematerial, said dyestuif being normally subject to acid fading uponexposure to an acid atmosphere in an aqueous medium comprising at least60% by weight of a lower aliphatic alcohol, a salt of thiocyanic acidwhich is a swelling agent for the cellulose acetate material and from 1to 4 grams per liter of potassium hydroxide.

6. Process for the coloration of cellulose acetate textile materials,which comprises mechanically impregnating said cellulose acetate textilematei rial with a solution of a dyestuff for the cellulose acetatematerial, said dyestuif being normally subject to acid fading uponexposure to an acid atmosphere in an aqueous medium comprising at least60% by weight of a lower aliphatic alcohol, a salt of thiocyanic acidwhich is a swelling agent for the cellulose acetate material, and from 1to 4 grams per liter of sodium hydroxide.

7. Process for the coloration of cellulose acetate textile materials,which comprises mechanically impregnating said cellulose acetate textilematerial with a solution of a dyestufi for the cellulose acetatematerial, said dyestuif being normally subject to acid fading uponexposure to an acid atmosphere in an aqueous medium comprising at least60% by weight of ethyl alcohol, a salt of thiocyanic acid which is aswelling agent for the cellulose acetate material, and from 1 to 4 gramsper liter of sodium hydroxide.

8. Process for the coloration of cellulose acetate textile materials,which comprises mechanically impregnating said cellulose acetate textilematerial With a solution of a dyestuif for the cellulose acetatematerial, said dyestufi being normally subject to acid fading uponexposure to an acid atmosphere in an aqueous medium comprising at least60% by weight of ethyl alcohol, from 1 to 3% by weight on the bath ofsodium thiocyanate, and from 1 to 4 grams per liter of sodium hydroxide.

WALTER H. HINDLE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,914,945 Ellis June 20, 19331,955,796 Ellis Apr. 24, 1934 2,017,119 Ellis Oct. 15, 1935 2,428,835Croft Oct. 14, 1947 FOREIGN PATENTS Number Country Date 295,579 GreatBritain Oct. 17, 1929 579,718 Great Britain Aug. 13, 1946

1. PROCESS FOR THE COLORATION OF ORGANIC ACID ESTER OF CELLULOSE TEXTILEMATERIALS, WHICH COMPRISES MECHANICALLY IMPREGNATING SAID ORGANIC ACIDESTER OF CELLULOSE TEXTILE MATERIAL WITH A SOLUTION OF A DYESTUFF FORTHE ORGANIC ACID ESTER OF CELLULOSE MATERIAL, SAID DYESTUFF BEINGNORMALLY SUBJECT TO ACID FACING UPON EXPOSURE TO AN ACID ATMOSPHERE INAN AQUEOUS MEDIUM COMPRISING A LOWER ALIPHATIC ALCOHOL, A SALT OFTHIOCYANIC ACID WHICH IS A SWELLING AGENT FOR THE ORGANIC ACID ESTER OFCELLULOSE MATERIAL AND FROM 1 TO 4 GRAMS PER LITER OF AN ALKALI METALHYDROXIDE.